1. Field of the Invention
The present invention relates to a method and apparatus for boiling wort in a beer brewing process.
2. Description of Related Art
In brewing, wort refers to the clear, liquid end product which results at the end of the refining process in the production of beer. In the conventional beer brewing process the wort is boiled to expel unwanted volatile aromatic substances in the boiling vapors. The wort boiling is also used for coagulation of the protein contained in the wort, destruction of the malt enzymes, sterilization of the wort, and isomerization of bittering hops. In addition, desirable aromatic substances are formed during the wort boiling.
In one classical brewing method used in particular in small and medium-sized breweries, the wort is introduced into a wort kettle in which the wort is boiled in a discontinuous, i.e., batchwise, manner. The wort vapor generated during boiling of the wort is discharged via the vapor outlet for the wort kettle. In addition, particularly in commercial brewing, methods are sometimes used in which the wort is boiled in a continuous flow.
The energy costs represent a significant cost factor in conventional beer production. Thus, the average heat requirements for the brewing process are approximately 145 to 185 MJ/hL of beer sold. The wort preparation, at 81 to 128 MJ/hL of beer sold, accounts for the greatest energy expenditure, so that achieving an energy-saving wort boiling method represents a significant opportunity for economizing.
It is known from M. Hertel, “Untersuchungen zum Ausdampfverhalten von Aromastoffen bei der Würzekochung aus verfahrenstechnischer Sicht,” Jahrbuch 2002 der Freunde des Lehrstuhls für Maschinen-und Apparatekunde e.V.,” a publication of the Chair for Mechanical and Equipment Engineering, Munich Technical University, 2002, to prepare the wort by rectification of the wort in order to increase the volatile components of the wort aromatic substances in the vapor and thus reduce the overall evaporation.
In brewing, rectification has been used heretofore in wort boiling in the form of a stripping process, in which the wort is continuously introduced into the head region of a stripping column, and while flowing inside this column is impinged in counterflow with inert gas or steam. The term “rectification” or “countercurrrent distillation” generally refers to a thermal/chemical separation process in which multiple distillation steps are discretely or continuously provided in succession by means of counterflow of two phases, in particular a vapor phase and a liquid phase in direct contact therewith. At the contact surface between the downwardly flowing wort and the counterflowing steam, volatile aromatic substances are absorbed by the steam and are thus removed from the wort. However, such methods as known from DE 31 26 714 A1, U.S. Pat. No. 4,550,029, WO 95/26395, and WO 97/15654 A1, for example, are relatively costly to implement, and therefore are generally economically feasible only in large-scale commercial brewing but not in small and medium-sized breweries.
A further disadvantage of the known stripping process is that during circulation of the wort through the stripping column, solid wort residues are deposited in the column, in particular at the column fittings. The column thus becomes contaminated and must be cleaned at frequent intervals. Since the fittings for a rectification column typically have a relatively finely branched structure, such a cleaning process entails significant effort.